Baffle type silencer with a buffer chamber



June 16, 1953 E. R. DEARING BAFFLE TYPE SILENCER WITH A BUFFER CHAMBERFiled Oct. 5, 1951 rig-a,

Patented June 16, 1953 BAFFLE TYPE SILENCER WITH A BUFFER CHAMBER EdmundR. Dearing, Homewood, Ala., assignor to United States Steel Corporation,a corporation of New Jersey Application October 3, 1951, Serial No.249,530

8 Claims.

upon an increase in the pressure in the main above the safe limit,quickly releases a large quantity of compressed air whichinstantaneously creates a level of noise utterly intolerable to personsin. the vicinity, continuing so long as the valve remains open. In fact,the noise may reach a level as high as twenty decibels whereas a levelof sixteen decibels is generally considered to be about the maximum forhuman tolerance. A faint indication of the seriousness of the nuisancemay be obtained by recalling the noise attributable to the relief of thepressure line of the ordinary portable compressor used in street andhighway maintenance which, of course, has only a minute fraction of theair capacity required for a blast furnace.

The noise condition referred to is aggravated by the induced vibrationof adjacent non-rigid members such as duct or pipe lines and thereverberation between buildings or other objects likely to be found inthe highly congested mill area in which the valve is usually located.The problem of reducing the noise level is complicated by the fact that,when the relief valve opens, one long continuous air blast of largevolume occurs. ly, furthermore, under ordinary conditions, and theterrifying efiect of such great noise at relatively long intervals mayeasily be imagined. The only solution for this problem offered by theoutstanding specialists in the silencer field intigue, i. e., sixteendecibels. Further objects are to provide a silencer of low cost and highefiiciency which is self-supporting and takes up but little ground area.In a preferred embodiment, I utilize a combination of partitions andbaffles defining a series of expansion chambers effective The valveopens only infrequentto relieve the pressure of the air graduallywithout excessive noise or vibration. More specifically, I provide ahousing'tube closed at one end and an outlet tube extending coaxiallypart way into the other end. An inlet pipe enters the housing tube anddischarges toward the closed end thereof where a buffer chamber isprovided. Ports spaced along the outlet tube, in combination with abaffle and partitions therein, cause the air to escape by a circuitouscourse whereby its pressure is reduced and its energy is graduallyconsumed and it is eventually released to the atmosphere at a relativelylow pressure and velocity.

A complete understanding of the invention may be obtained from thefollowin detailed description and explanation which refer to theaccompanying drawings illustrating the present preferred embodiment. Inthe drawings,

Figure l is a vertical axial section showing parts in elevation; and

Figure 2 is a transverse section taken along the plane of line IIII ofFigure 1.

Referring now in detail to the drawings, a silencer indicated generallyat Ill stands on a foundation H adjacent a cold-blast main [2 such asthat extending from the blower house to the stoves of a blast-furnace.The main is equipped with a relief valve 13. The silencer it! comprisesa housing tube 14 having a base plate 15 closing the low-er end thereofand an outlet tube It open at the top, extending coaxially part way intothe upper end of tube l4 and having a peripheral flange l1 restingthereon. The lower end of tube It extends through a baffie or partitionl8 carried by tube It, with a sliding fit therein, and has a transversewall or closure I 9 adjacent its extremity. A transverse wall orpartition 20 is disposed in tube 16 between the baffle l3 and the upperend of tube l4. Tube is should extend to a height greater than that ofadjacent buldings or other structures.

Ports in the form of elongated slots 2| are spaced circumferentially andlongitudinally of the wall of tube l6 below baffle i8. Similar .ports 22but of greater aggregate area are located be tween battle i8 andpartition 26. Similar ports 23 of still greater aggregate area arelocated between partition 30 and the upper end of tube I4. All the portsare of about the same Width ut the length and numb-er of ports in thesuccessive groups increase upwardly. Baflle l8 and walls 9 and 20 definesuccessive expansion stages it for the compressed air, each stagecomprising one of the groups of ports 2 l, 22 and 23.

An orifice plate 24 is disposed in tube [4 adjacent the lower endthereof but spaced above plate l5, defining a capacitance or bufierchamber I5a at the bottom of the tube. An inlet pipe 25 enters tube I4from one side, at about the level of the lower end of tube It, andincludes an elbow whereby it discharges directly toward the orifice inplate 24. Pipe 25 is connected to an outlet pipe 26 from valve l3through a non-metallic sleeve 21 which is flexible and yieldable so asto prevent vibrations from being transmitted from the valve to silencerM].

In explaining the operation of the invention-it will be assumed thatvalve l3 opens in response to excess blast-main pressure which may becaused by the closing or throttling of air valves at the furnace or someother reason. The excess air escapes from main l2 through the valve andits outlet pipe 26 to silencer inlet 25 and is discharged toward thecapacitance or buffer chamber Mia. The air expands in tube Hi and pipe25 directs a jet through the orifice in plate M. The space below thelatter functions as an acoustical capacitance chamber which has theeffect of a low-pass filter. The air in chamber l 5a, furthermore, actsas a buffer or cushion to air pulses from inlet 25. When the pressure onopposite sides of plate 2t is equalized, the entering air is divertedupwardly as shown by the arrows, and floWs' outside the entering jet andin countercurrent'relation thereto.

Air ascending through tube M passes around the entering jet, entersoutlet tube 56 through ports 2i and is there permitted to expandfurther. The shape and distribution of the ports subdivides the hollowascending air stream into a multiplicity, say eighteen, of wide, thinstreams. These are further subdivided on flowing out through ports 22for further expansion in the space between tubes i4 and 25 above bafflei3. Ports 22 may number twenty-six, for example. The air then re-enterstube it through ports 23 of which there may be twenty-eight, for finalexpansion to atmospheric pressure and discharge through the upper openend of the tube.

Tube i6 is dimensioned to have a fundamental resonant frequency of 16cycles per second or below so that the escaping air produces only alow-pitched rumble. The intensity thereof is reduced to a level belowsixteen decibels (actually around eleven decibels) ind so causespractically no annoyance to those in the vicinity. The reduction in theenergy content of the escaping air results from its gradual expansionand repeated passage around the sharp edges of the ports in tube I 6caused by bafile l8 and walls l9 and 253. The progressive increase inthe size and number of the ports in the several groups scatters thefrequencies of the sound waves produced, tending to cause multipleinterference rather than reinforcement of any particular frequency. Thecapacitance chamber tends to trap high-frequency vibrations whilepermitting low-frequency sounds to escape.

It will be apparent that the invention is characterized by manyimportant advantages. It is remarkably effective in reducing the noiseof a large volume of escaping compressed air, from an overpowering,nerve-wracking and deafening intensity to a level well below that whichcan oomfortably be tolerated and further to a level which is not evendisturbing. Such sound as is procluced is directed upwardly and isreadily dissipated. The structure is simple, compact, selfsupporting andrelatively inexpensive. When once installed, it requires no maintenancebeyond that of any steel structure exposed to the weather. The devicecan easily be incorporated in existing plants without major alterations.j

While the invention has been disclosed with particular reference to therelief valve of a blast main for a blast-furnace, it will be understoodthat it is applicable generally to a compressor, receiver or anyinstallation where large volumes of gas under pressure are releasedsuddenly to the atmosphere.

Although I have disclosed herein the preferred embodiment of myinvention, I intend to cover as well any change or modification thereinwhich may be made without departing from the spirit and scope of theinvention.

I claim:

1. A silencer comprising a housing tube, a closure at one end thereof,an outlet tube smaller in diameter than the housing tube extendingcoaxially into the other end of the latter but terminating short of theclosed end thereof, an inlet pipe entering said housing tube from oneside adjacent the inner end of the outlet tube and discharging towardthe closed end of the housing tube, the portion of the outlet tubewithin the housing tube having ports spaced therealong, a baflle spacedfrom the inner end of the outlet tube closing the space between thetubes and transverse walls in the outlet tube spaced axially in bothdirections from said ,bafile whereby gas entering the housing tube iscaused to execute successive passes through said ports into and out ofsaid outlet tube.

2. The apparatus defined by claim. 1 characterized by said outlet tubebeing secured to said other end of the housing tube and free to slidethrough said baffle.

3. The apparatus defined by claim 1 characterized by an orifice plate insaid housing tube adjacent the closed end but spaced therefrom.

4:. A silencer comprising a housing tube, a closure at one end thereof,an inlet entering said tube from one side and discharging toward saidclosure, an outlet tube smaller in diameter than the housing tubeextending coaxially into the other end of the latter but terminatingshort of the closed end thereof, a closure on the inner end of saidoutlet tube, a partition in said outlet tube disposed inwardly of saidother end of the housing tube and spaced from said closure, ports spacedcircumferentially and longitudinally of the outlet tube and a bafileclosing the space between the housing tube and the outlet tube at apoint between the closure and partition of the outlet tube. v

5. A silencer comprising a housing tube having a closure at oneend, aninlet entering said tube from one side and discharging toward saidclosure, an outlet tube smaller in diameter than the housing tubeextending coaxially into the other end of the latter, a closure on theinner end of the outlet tube, a baffle closing the space be tween theoutlet tube and the housing tube adjacent the inner end of the outlettube, a trans verse partition in said outlet tube between said bafileand'said other end of the housing tube and ports in said outlet tube onboth sides of said baffle and said partition. 6. The apparatus definedby claim 5 characterized by said outlet tube having a sliding fit insaid bafile.

7. The apparatus defined by claim 5 characterized by means defining abuffer chamber in the closed end of said housing tube.

8. The apparatus defined by claim 7 characterized by said means being anorifice plate.

EDMUND R. DEARIN G.

References Cited in the file of this patent UNITED STATES PATENTS NameDate Kersey May 24, 1932 Number Number Number Name Date Rauen Feb. 24,1942 Rauen Feb. 24, 1942 Wohlberg Dec. 14, 19% Hoyle et a1 June 13, 1959FOREIGN PATENTS Country Date Germany Nov, 12, 1937 Sweden June 23, 1942

